Absolutely brilliant. Tour de force of masterful absurdity, the treasury of paradoxes, the bliss of irony and humor. I first read Dimension of Miracles some 30 years ago as a teenager and enjoyed it back then, but now I am totally infatuated with it's sheer brilliance. It was written before The Hitchhiker's Guide to the Galaxy, and Douglas Adams claimed he read it only after he wrote the Guide, but the similarity of tone and mood is amazing. This may be a dangerous thing to say, but I think that Dimension of Miracles is deeper and richer beneath the same light tone sparkling with paradoxes and irony it shares with the Guide. It's a short book, but it has multiple dimensions(just like it's title) and is packed with thought provoking delights.
It's a shame that with the exception of the recently released audio book Dimension of Miracles seems to be more easily obtainable and better known in many non-English speaking countries of Europe (France, Russia, Italy, Spain) than in US or UK.